Those old phones did not use much electricity. You could run a new smartphone only for a few seconds using many, many of these old batteries in a massive serial+parallel setup. Screen size? 80×40 only a few thousand pixels, black and white with terrible framerate. A monochrome display‎, capable of showing 5 lines of pixelated text. Today 1080p means 2 million pixels, 16 million colors each, and 60/120 FPS. Separate video card, wifi chip, biometrics, multi-tasking, hundreds of apps running in background, etc. And processors: Old phones had Single-Core ARM7-TDMI running at 20-40 MHz Today, dual/quad/hexa -core at 2000 MHz is the minimum.﻿